P1.2 Flashcards
change of state
the process of moving from one physical state to another, for example, melting
chemical reaction
process in which substances react to form different substances
degree Celsius (°C)
a unit of temperature
density
mass/volume, usually measured in kg/m3
The density depends on the mass and the volume.
If you have two identically sized blocks of different material, the one with the bigger density will have a bigger mass. Density does not depend on the volume of material that you have.
internal energy
the energy of a system because of the arrangement and movement of particles in it
joule (J)
the unit of energy
kelvin (K)
a unit of temperature
mass
the amount of matter, usually measure in kilograms
physical change
change, such as a change in state, that does not result in new substances being made
specific heat capacity (J/kgK)
the energy required to raise the temperature of 1 kg of a substance by 1 K
change in thermal energy (J) / [mass (kg) x change in temperature (°C)]= specific heat capacity (J/kg °C)
specific latent heat of fusion (or melting)
the energy required to fuse or melt 1 kg of a substance
Assuming that the energy transferred to each liquid is the same, a high specific latent heat will mean that only a small mass of liquid will change state.
specific latent heat of vaporisation
the energy required to vaporise of condense 1 kg of a substance
temperature
a measure of the average kinetic energy of the particles in a material. It does not depend on the amount of the material that you have
volume
the amount of space an object takes up, usually measure in m3
compare the meanings of density and mass.
The density depends on the mass and the volume.
If you have two identically sized blocks of different material, the one with the bigger density will have a bigger mass. Density does not depend on the volume of material that you have.
the density equation
calculate values for mass, volume, and density using the density equation.
density (g/cm^3) = mass (g) / volume (cm^3)
Model to explain differences in density.
Fill the tray with marbles in a regular pattern to model a solid. Make measurements using the ruler and digital balance to find the density of a ‘marble solid’. Repeat the experiment with ball bearings, and polystyrene balls.
Now repeat the experiment with the marbles, but this time rearrange the marbles so there are more marbles in the tray. Work out how to have a regular pattern of marbles but with less space between them. Repeat the measurement of mass and work out the new density.
Now make a ‘marble liquid’ and measure its density.
density (number/cm^3) = number of balls / volume (cm^3).
Improvement?
Improvement: Use different types of ball e.g. ball bearings/polystyrene balls. This shows that different types of material have particles/atoms/molecules with different masses.
explain the difference between temperature and the energy in a thermal store using the particle model.
The temperature rise depends on the mass, specific heat capacity and the energy transferred
The mass is proportional to the volume because the density is constant. The energy transferred to the water is proportional to the time. If the power/energy transferred per second by the flame is constant.The specific heat capacity of the water is constant so the time should be proportional to the volume.
the change in thermal energy increases in proportion to the volume, but the time does not which suggests that the energy per second is not constant.
why it is useful to know the specific heat capacity of a material.
As the volume of water increases, the time it takes to heat the water by 1°C increases because as the volume increases the mass increases so the number of particles increases so it takes longer to increase the internal energy of the liquid/average energy of each particle.
I can rearrange the specific heat capacity equation and use it in calculations.
change in thermal energy (J) = mass (kg) x specific heat capacity (J/kg °C) x change in temperature (°C)
explain the differences in density of a substance in its different states using the particle model.
Liquids are less dense than solids because the particles are further apart and the volume is larger so the density is smaller. Gas has the smallest density because the particles are furthest apart.
The number of particles in a given volume for a liquid is smaller than for a solid.
You have 0.1 kg of water, which has a volume of 100 cm3. You heat it so that the temperature rises by 10 °C. The specific heat capacity of water is 4200 J/kg °C. Calculate the change in thermal energy:
0.1 kg x 4200 J/kg °C x 10 °C = 4200 J
Explain why the time to heat 100 cm3 of a different liquid by 10 °C is different to that of water.
There may be more or fewer particles/particles of a different mass so you need to transfer a different amount of energy to increase the internal energy of the liquid/average energy of each particle.
Investigate the change in mass of different liquids.
Put 100 cm3 of a liquid into a dish in a fume cupboard and leave for 10 minutes to find change in mass of liquid.
Improve the model to show the densities of different types of solid material.
Use different types of ball e.g. ball bearings/polystyrene balls. This shows that different types of material have particles/atoms/molecules with different masses.
Investigate the change in mass of different liquids.
Put 100 cm3 of a liquid into a dish in a fume cupboard and leave for 10 minutes to find change in mass of liquid.
Suggest one advantage and one disadvantage of using this method to model solids and liquids.
Advantage: you can see the particle arrangements.
Disadvantage: difficult to accurately model solids because it is difficult to make it in 3D/difficult to model liquids in 3D.
Heat 100 cm3 of water into the beaker and start the stop clock at the same time. When the temperature of the water has risen by 10 °C switch off the stop clock. Record the time in seconds for temperature to rise by 10 oC.
Plot a graph of time against volume of water.
Describe and explain the shape of your graph of time against volume of liquid.
As the volume of water increases the time it takes to heat the water by 10 °C increases because as the volume increases the mass increases so the number of particles increases so it takes longer to increase the internal energy of the liquid/average energy of each particle.
Aluminium has a density of 2.71g/cm^3.
How much does a 1m3 weigh in kg
2710kg
Aluminium has a density of 2.71g/cm^3.
Calculate the volume of 420kg in m^3
Weight/mass = volume
0.155m^3
The specific latent heat of acetone is 518 kJ/kg. Calculate the change in thermal energy of 56g acetone in this experiment. Make sure that you use standard units in your calculation.
Specific latent heat = 518 kJ/kg = 518 000 J/kg
Change in mass = 5.6 g = 0.0056 kg.
thermal energy for a change in state (J) = mass (kg) x specific latent heat (J/kg)
= 0.0056 kg x 518 000 J/kg = 2900 J
Model to explain differences in density.
Fill the tray with marbles in a regular pattern to model a solid. Make measurements using the ruler and digital balance to find the density of a ‘marble solid’. Repeat the experiment with ball bearings, and polystyrene balls.
Now repeat the experiment with the marbles, but this time rearrange the marbles so there are more marbles in the tray. Work out how to have a regular pattern of marbles but with less space between them. Repeat the measurement of mass and work out the new density.
Now make a ‘marble liquid’ and measure its density.
density (number/cm^3) = number of balls / volume (cm^3)
Advantages and disadvantages:
Advantage: you can see the particle arrangements.
Disadvantage: difficult to accurately model solids because it is difficult to make it in 3D/difficult to model liquids in 3D.
Model to explain differences in density.
Fill the tray with marbles in a regular pattern to model a solid. Make measurements using the ruler and digital balance to find the density of a ‘marble solid’. Repeat the experiment with ball bearings, and polystyrene balls.
Now repeat the experiment with the marbles, but this time rearrange the marbles so there are more marbles in the tray. Work out how to have a regular pattern of marbles but with less space between them. Repeat the measurement of mass and work out the new density.
Now make a ‘marble liquid’ and measure its density.
density (number/cm^3) = number of balls / volume (cm^3)
The density of the marble ‘solid’ is greater than the density of the marble ‘liquid’. The number of particles in a given volume for a liquid is smaller than for a solid.
Model to explain differences in density.
Fill the tray with marbles in a regular pattern to model a solid. Make measurements using the ruler and digital balance to find the density of a ‘marble solid’. Repeat the experiment with ball bearings, and polystyrene balls.
Now repeat the experiment with the marbles, but this time rearrange the marbles so there are more marbles in the tray. Work out how to have a regular pattern of marbles but with less space between them. Repeat the measurement of mass and work out the new density.
Now make a ‘marble liquid’ and measure its density.
density (number/cm^3) = number of balls / volume (cm^3)
Heat 100 cm3 of water into the beaker and start the stop clock at the same time. When the temperature of the water has risen by 10 °C switch off the stop clock. Record the time in seconds for temperature to rise by 10 oC and
Validity/control variables?
Repeat for different volumes of water in cm3. Stir each time. Same starting temp. Using similar Bunsen flame temp.
Heat 100 cm3 of water into the beaker and start the stop clock at the same time. When the temperature of the water has risen by 10 °C switch off the stop clock. Record the time in seconds for temperature to rise by 10 oC and
Improvement
If available, heat 100 cm3 of a different liquid until the temperature has risen by 10 °C.
The student used the same volume of each liquid, and the mass of the dishes was the same. Explain why the change in the mass of liquid was not the same in each case.
The densities of the liquids are different. The thermal energy transferred to the liquid was the same in each case but the specific latent heats are different so different masses evaporated.
Specific latent heat
Specific latent heat is the energy required to change the state of 1 kg of material. Assuming that the energy transferred to each liquid is the same. A high specific latent heat means that a large thermal energy transfer produces a change of state of a small mass of liquid.
A low specific latent heat means that you have to run the compressor for longer.
